The present invention relates to a heat transfer medium having a high heat transfer rate, a heat transfer surface, and a heat transfer element utilizing the heat transfer medium.
Efficiently transporting heat from one location to another always has been a problem. Some applications, such as keeping a semiconductor chip cool, require rapid transfer and removal of heat, while other applications, such as dispersing heat from a furnace, require rapid transfer and retention of heat. Whether removing or retaining heat, the heat transfer abilities of the material utilized define the efficiency of the heat transfer.
For example, it is well known to utilize a heat pipe for heat transfer. The heat pipe operates on the principle of transferring heat through mass transfer of a fluid carrier contained therein and phase change of the carrier from the liquid state to the vapor state within a closed circuit pipe. Heat is absorbed at one end of the pipe by vaporization of the carrier and released at the other end by condensation of the carrier vapor. Although the heat pipe improves thermal transfer efficiency as compared to solid metal rods, the heat pipe requires the circulatory flow of the liquid/vapor material and is limited by the material""s vaporization and condensation temperatures. Consequently, the heat pipe""s axial heat transfer rate is further limited by the magnitude of the material""s latent heat of liquid vaporization and the rate of transformation between liquid and vapor states. Further, the heat pipe is convectional in nature and suffers from thermal losses, thereby reducing the thermal efficiency. It is generally accepted that when two substances having different temperatures are brought together, the temperature of the warmer substance decreases and the temperature of the cooler substance increases. As the heat travels along a heat conducting conduit from a warm end to a cool end, available heat is lost due to the heat conducting capacity of the conduit material, the process of warming the cooler portions of the conduit and thermal losses to the atmosphere.
I disclose a heat transfer composition and the method for its preparation in U.S. Pat. No. 6,132,823, issued Oct. 17, 2000.
In that patent, the heat transfer medium was made up of three layers deposited on a substrate. The first two layers were prepared from solutions exposed to the inner wall of the conduit. The third layer was a powder comprising various combinations. The first layer was placed onto an inner conduit surface, the second layer was then placed on top of the first layer to form a film over than inner conduit surface. The third layer was a powder preferably evenly distributed over the inner conduit surface.
The first layer was nominated an anti-corrosion layer to prevent etching of inner conduit surface. The second layer was said to prevent the production of elemental hydrogen and oxygen, thus restraining oxidation between oxygen atoms and the conduit material. The third layer, referred to as the xe2x80x9cblack powderxe2x80x9d layer, was said to be activated once exposed to a minimum activation temperature of 38xc2x0 C. Consequently, it was said elimination of any of the three layers from the prior heat transfer medium might have an adverse effect on heat transfer efficiency.
In addition, the method for preparing the prior medium was complicated and cumbersome. For instance, formation of the first layer might involve nine chemical compounds prepared in seven steps. Formation of the second layer might involve fourteen compounds prepared in thirteen steps. Formation of the third layer might involve twelve compounds prepared in twelve steps. In addition, if the components of each layer were combined in an order not consistent with the listed sequence and conforming to the exceptions noted in my patent, the solutions made for such preparation were potentially unstable.
Generally, the heat transfer medium of the present invention eliminates or improves upon many of the noted shortcomings and disadvantages. The heat transfer medium of the present invention preferably is made up of a layer, most preferably a single layer, deposited on a substrate, prepared from a group of twelve inorganic compounds selected from the list below and formed in a single layer. The improved medium not only reduces the number and types of compounds used in the medium, but also effectively reduces the number of steps required for the preparation of the medium without compromising heat transfer efficiency.
The present invention provides a high heat transfer rate heat transfer medium that is useful in even wider fields, is simple in structure, easy to make, environmentally sound, and rapidly conducts heat and preserves heat in a highly efficient manner.
The present invention provides a heat transfer medium, typically inorganic in nature, which is a composition. The composition comprises or, in the alternative, consists essentially of the following compounds mixed together in the ratios or amounts shown below. The amounts may be scaled up or down as needed to produce a selected amount. Although the compounds are preferably mixed in the order shown, they need not be mixed in that order.
Cobaltic Oxide (Co2O3), 0.5%-1.0%, preferably 0.7-0.8%, most preferably 0.723%;
Boron Oxide (B2O3), 1.0%-2.0%, preferably 1.4-1.6%, most preferably 1.4472%;
Calcium Dichromate (CaCr2O7), 1.0%-2.0%, preferably 1.4-1.6%, most preferably 1.4472%;
Magnesium Dichromate (MgCr2O7xc2x76H2O), 10.0%-20.0%, preferably 14.0-16.0%, most preferably 14.472%;
Potassium Dichromate (K2Cr2O7), 40.0%-80.0%, preferably 56.0-64.0%, most preferably 57.888%;
Sodium Dichromate (Na2Cr2O7),10.0%-20.0%, preferably 14.0-16.0%, most preferably 14.472%;
Beryllium Oxide (BeO), 0.05%-0.10%, preferably 0.07-0.08%, most preferably 0.0723%;
Titanium Diboride (TiB2), 0.5%-1.0%, preferably 0.7-0.8%, most preferably 0.723%;
Potassium Peroxide (K2O2), 0.05%-0.10%, preferably 0.07-0.08%, most preferably 0.0723%;
A selected metal or ammonium Dichromate (MCr2O7), 5.0%-10.0%, preferably 7.0-8.0%, most preferably 7.23%, where xe2x80x9cMxe2x80x9d is selected from the group consisting of potassium, sodium, silver, and ammonium.
Strontium Chromate (SrCrO4), 0.5%-1.0%, preferably 0.7-0.8%, most preferably 0.723%; and,
Silver Dichromate (Ag2Cr2O7), 0.5%-1.0%, preferably 0.7-0.8%, most preferably 0.723%.
The percentages expressed just above are weight percentages of the final composition once the composition has been dried to remove the added water.
The present invention also provides a heat transfer surface comprising a surface substrate covered at least in part by the high heat transfer rate inorganic heat transfer medium of the present invention.
The present invention also provides a heat transfer element comprising the high heat transfer rate inorganic heat transfer medium situated on a substrate.
The objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiments thereof in connection with the accompanying drawings, in which like numerals designate like elements.